I LOVE THIS. The idea is amazing and executed so well. The game is a bit tricky at the beginning, but once you get the hang of it, it's WORTH it!
I love the idea of "upkeep" and undermining the city. The game is difficult, but that's what I love about it. :) Great graphics and very creative.
The only thing I would change about it is that once you get to turn 20, the game turns very difficult. Awesome job!